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Municipal Bond Guarantee (Tables) | 9 Months Ended
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Sep. 30, 2018
Guarantees [Abstract] |
Schedule of Municipal Bond Guarantee Insured Obligations | The following table presents a schedule of BAM’s insured obligations:
|  | September 30, 2018 |  | December 31, 2017
Contracts outstanding |  | 7,184 |  |  | 6,371 |
Remaining weighted average contract period outstanding (in years) |  | 10.8 |  |  | 10.9 |
Contractual debt service outstanding (in millions): |  |  |  |
Principal |  | $ | 47,259.1 |  |  | $ | 42,090.6 |
Interest |  | 23,707.4 |  |  | 21,057.1 |
Total debt service outstanding |  | $ | 70,966.5 |  |  | $ | 63,147.7 |
Gross unearned insurance premiums |  | $ | 156.2 |  |  | $ | 136.8 |
Financial Guarantee Insurance Contracts, Premium Received over Contract Period | The following table presents a schedule of BAM’s future premium revenues as of September 30, 2018:
Millions |  | September 30, 2018
October 1, 2018 - December 31, 2018 |  | $ | 3.3 |
January 1, 2019 - March 31, 2019 |  | 3.3 |
April 1, 2019 - June 30, 2019 |  | 3.3 |
July 1, 2019 - September 30, 2019 |  | 3.3 |
October 1, 2019 - December 31, 2019 |  | 3.2 |
Total 2019 |  | 13.1 |
2020 |  | 12.6 |
2021 |  | 12.1 |
2022 |  | 11.5 |
2023 and thereafter |  | 103.6 |
Total gross unearned insurance premiums |  | $ | 156.2 |
Schedule of Net Written Premiums | The following table presents a schedule of net written premiums included in White Mountains’s HG Global/BAM segment for the three months years ended September 30, 2018 and 2017:
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
Millions |  | 2018 |  | 2017 |  | 2018 |  | 2017
Gross written premiums |  | $ | 3.9 |  |  | $ | 10.9 |  |  | $ | 28.9 |  |  | $ | 42.0 |
Assumed (ceded) written premiums |  | — |  |  | — |  |  | — |  |  | — |
Net written premiums |  | $ | 3.9 |  |  | $ | 10.9 |  |  | $ | 28.9 |  |  | $ | 42.0 |

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- Definition Tabular disclosure of financial guarantee insurance contracts in which premiums are received over the contract period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290 + Details
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- Definition [Table Text Block] for Schedule of Municipal Guarantee Insured Obligations [Table] + References No definition available. + Details
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